The invention relates generally to locking mechanisms for controlling access to shared data storage resources.
Today, data storage systems are commercially available that provide many gigabytes of data storage capacity and that permit multiple host processors to connect to and access that storage. The Symmetrix Model 55XX series which is sold by EMC Corporation of Hopkinton, Mass. is one example of such a system. The Symmetrix is a high performance Integrated Cache Disk Array (ICDA) that is designed for online storage. As is typical of other of the commercially available designs, the Symmetrix Model 55XX includes a large array of smaller storage (e.g. 51/4 inch) disk devices and a cache for temporarily storing data which is transferred into and out of the data storage system. In the Model 55XX there can be as many as 128 such disk devices. Each individual disk device is capable of storing from 2 to 9 GB. Thus, the total storage capacity of the system is in the hundreds of Gigabytes.
In the Symmetrix Model 55XX ICDA's one is able to define a portion of the data storage area that is shared by two or more of the host processors that are connected to the system. If the host processors that are able to access files in the shared storage area are all running UNIX operating systems, a problem can occur. Since one Unix system does not know anything about what another Unix system might be doing, it is very possible to corrupt shared files. That is, recently updated data in one file can be inadvertently overwritten by another host processor that is connected to the data storage system.
The invention described below solves this problem, not only for a group of host processors running homogeneous operating systems (e.g. UNIX based systems) but also for any group of host processors that are running heterogeneous operating systems.